Conventional sealing means for sealing interspaces, such as rubber seals, polymer seals, adhesive means, or engaging of a projection in a slot, as are especially to be encountered in the case of the seal between two static elements, are generally known. In gas turbines, a wide variety of elements are cooled by means of a cooling air flow for avoiding heat damage. This cooling air flow is to be effected with the lowest losses possible in order to maximize the cooling potential. A plurality of types of sealing for sealing interspaces in gas turbines are known from the field of the present invention (for example GB 2 420 162, U.S. Pat. No. 5,797,723). Such types of sealing, however, in gas turbines between two components which are movable relative to each other, such as between a rotor element and a stator element, or between two components which must have a certain clearance, are poor in application.
In order to achieve an efficient seal between two blade elements in a gas turbine, for example in order to prevent the loss of cooling air as a result of a leakage flow, a precise matching of the blade elements to each other is necessary. If, however, the wish is to make a certain “clearance” possible for the abutting components, which is indispensable for example between two rotor blades in a rotor of a gas turbine on account of the intense flow around the blade elements by hot operating medium during operation, a precise, clearance-free matching of two adjacent shrouds of blade elements is almost impossible since such a compact type of construction, as would be necessary for the complete sealing of the radial gap, can lead to problems, for example on account of thermal expansion. Also, the effect of centrifugal forces between the components after installation can be considerable, which can lead to severe wear of conventional sealing means (as is described for example in DE 199 31 765 A1). For these reasons, so-called “shiplaps” are used between blades in a gas turbine rotor according to conventional design for sealing the leakage flow in the axial direction. “Shiplaps” constitute a thermally resistant sealing means since they are designed essentially from the material of the blade elements themselves, form an integral component part of the blade elements, and therefore enable a sealing effect without additional material which is possibly sensitive to heat or has a different coefficient of thermal expansion.
Turbine blades, especially low-pressure turbine blades, in most cases have at least one shroud element radially on the inside and/or radially on the outside, which, with the blade row installed, abut on the respectively adjacent shroud element of the respectively adjacent blade element by the two sides of the shroud element which point in the circumferential direction, forming in each case an essentially radial gap. Such a turbine blade element, on at least one axial edge, especially the trailing edge, on a first side which points in the circumferential direction, can have a projection which extends in the circumferential direction and projects into the shroud element of the abutting blade element, and on a second side which points in the circumferential direction can have a recess which accommodates this projection.
The sequential installation of such blade elements leads in each case to the forming of a so-called “shiplap” between two blade elements. Such a shiplap is an overlapping or engaging region, which is stepped in the flow direction of the operating gas, between the shroud element on an axial edge of a blade element and the shroud element on the same axial edge of the adjacent blade element. This shiplap seals the radially extending gap between the contiguous circumferential sides of two turbine blades against the escape of cooling air from the secondary air circuit, i.e. against the leakage flow in the axial direction. Such a shiplap comes into being as result of the covering of a recess on a first side, which points in the circumferential direction, of an adjacent blade element by means of a projection on the second side, which points in the circumferential direction, of a blade element, or by the engagement of the projection in the recess. In U.S. Pat. No. 6,966,750, such a projection, and also a recess and the stepped overlaying or engagement region which results during installation, are shown in FIG. 13. The known conventional shiplap, however, is not able to fully seal the radial gap, for which reason a significant amount of cooling air can escape as a result of the stepped overlapping region. This loss results in reduced efficiency and output of the turbine.